When a joint, such as a knee or elbow joint, is immobilized while healing from an injury, after an operation, or as a result of disease, the soft tissues at the joint contract. Motion of the joint is limited both by actual physical restraint due to the soft tissues which have contracted and by psychological restraint due to the pain that is encountered when the soft tissues are stretched. However, to return the joint to its normal range of mobility the soft tissues must be stretched to increase the range of motion of the joint.
Stretching of the soft tissues is best carried out by passive manipulation of the joint since the muscles that operate the joint are in a weakened condition as a result of immobilization. During manipulation of the joint, pain will result as scar tissue and adhesions are broken off. The pain encountered during passive manipulation of the joint must be controlled and always held below the patient's allowable pain tolerance as exceeding a patient's pain tolerance can cause new adhesions to be formed and result in regression in the condition of the joint. Operation in a comfort zone within the patient's allowable pain tolerance is also important since stretching of the soft tissues is facilitated as the patient relaxes and tense muscles are overcome by weariness. To continually assure operation in the comfort zone, the stretching necessarily must be carried out gradually over an extended period of time.
The use of the apparatus of this invention to provide uniform and continuous mechanical therapy rather than depending solely upon manual therapy is desirable as it is impractical for a physical therapist to manually manipulate a joint for an extended period of time for several reasons. First, the therapist will not have the stamina to continue the treatment in a uniform and consistent manner for an extended period of time. However, the apparatus of this invention can provide continuous uniform treatment for an extended period. Secondly, the cost of treatment that would require a skilled physical therapist's constant attendance and total involvement for extended periods of time would be quite expensive. On the other hand, the apparatus of this invention can manipulate the joint over an extended period of time without the physical therapist being in attendance, resulting in lower cost for therapy. Thirdly, a skilled physical therapist must generally rely on a trial and error approach through his sense of feel to establish the range of motion of the joint that was attained in the previous treatment so as to use it as a starting point for the next treatment, to establish a specific desired angle through which the joint is reciprocated during treatment, and to establish a specific desired amount of force to be applied during the treatment. If a physical therapist exceeds the patient's pain tolerance, he may cause regression in the condition of the patient or at the very least cause pain and discomfort to the patient. However, the apparatus of this invention can be controlled so as to accurately and repeatably position the joint from one treatment to the next for a desired range of motion. Furthermore, the apparatus of this invention additionally permits accurate control of the angle through which the joint is reciprocated during passive manipulation of the joint and of the amount of force applied during the manipulation.